Probably fine then, most respectable porn sites are big businesses as somebody said above where a lot of money is made and if they serve malware then they lose reputation and money.

I read a study recently that suggested you were more likely to get malware from sites listed in the category religion, rather than porn as porn sites have a vested financial interest in keeping sites clean and securing against vulnerability, where as most church sites are run part time and by people with limited technical knowledge leading to them being much higher risk.

It's hard to see why an adult site would require you to install an ap. My friend tells me the content uses standard video formats. At most you woulfd need a bog standard video player. Some porn sites are fronts for all sorts of activities, and many simply link to other sites, so in general a "player" ap could be a keylogger or something that allows your device to forward kiddie porn, denial of service attacks, etc without revealing the source. I don't know the provider you mention but as a general principle play safe.

If the ap is well known close the porn site connection, go direct to the reputable manufacturer - Google, Apple, Microsoft - and download from there. Never ever download software from a porn site.